Collagen is used in a variety of medical applications ranging from hemostatic materials and biocompatible coatings to drug delivery and tissue engineering. Collagen-based biomaterials are presently used for soft-tissue engineering and repair, and medical products composed of collagen have been approved by the FDA, and are commercially available. These include collagen-based corneal shields, anti-infectious catheters, tissue sealants, hemostatic sponges, and topical wound dressing products. Collagen is also used for tissue engineering substrates targeted for skin, bone, and blood vessel replacement. There is increasing demand for biocompatible and biofunctional materials that feature collagen as a scaffold to support tissue growth, to promote healing, and to develop engineered tissues for organ replacement therapies.
Traditionally, collagen is used as a passive biomaterial that protects injured sites and supports healing processes. Methods for modifying collagen would be useful for the development of materials that can participate in tissue regeneration by actively regulating cell differentiation, proliferation, and tissue organization. Methods for producing modified collagens have focused on chemical modification, that include coupling modifying groups to collagen's amino acid side chains; however, the chemical reactions between exogenous components and collagen molecules are toxic and difficult to control because collagen molecules are large and complex biopolymers. Progress in the area of tissue repair and regeneration requires better methods for conjugating exogenous functionalities to collagen. Desirably, such methods should overcome challenges associated with controlling chemical reactions and chemical toxicity.